Patent GB-632403-A (GB)
Title: Improved method for selecting operations on a succession of articles
IPC: B65G47/50
Filed: 1947-07-18
Abstract: 632,403. Sorting letters &c. PIGGOTT, J. July 18, 1947, No. 19271. [Class 78 (i)] A method of selecting operations to be performed on a succession of articles according to their predetermined characteristics comprises delivering the articles one by one to a conveyer and simultaneously or at a constant interval after delivery of each article making a recording on a wire or tape moving in step with the conveyer corresponding according to a code with the predetermined characteristic of the article, converting each recording into an electric impulse, the nature of the impulse or the position in space at which it is generated being determined by the recording, and applying the impulse to means adapted to select an operation on the article at a point of the conveyer corresponding according to the nature and/or position in space of the impulse. The method as applied to sorting postal packets comprises a plurality of operator positions A<SP>1</SP>, B<SP>1</SP>, C<SP>1</SP>, D<SP>1</SP>, E<SP>1</SP> and F<SP>1</SP>, Fig. I, associated with each of which is a waiting position A<SP>2</SP> - F<SP>2</SP>, a queue position A<SP>3</SP> - F<SP>3</SP>, and a loading position A<SP>4</SP> - F<SP>4</SP> for loading letters onto a belt conveyer 30. All the operators are similarly equipped, e.g. operator A has a coding keyboard A<SP>5</SP>, Fig. 2, a viewing position A<SP>6</SP>, and automatic feed means A7 for advancing letters one by one from a stack into a feed position A<SP>8</SP> from which they can be shot into the viewing position A<SP>6</SP> as required, after which they are advanced to waiting position A2. The operators work independently of one another and of the belt 30 since letters coded are fed to a queue position A<SP>3</SP> to be fed automatically to the belt as space allows. The keyboard may comprise a combination of direct label keys for frequently occurring destinations and coded keys, two of which must be pressed for the remaining destinations. Control units A9, A<SP>10</SP> determine whether the correct number of keys have been depressed and if so allow power to be fed from power unit 31 to the keyboard and to means for advancing the letter in waiting position A<SP>2</SP> to queue position A3, the coded letter being advanced from A<SP>6</SP> to A2, and a letter from the stack to A<SP>6</SP>. An electric signal is then generated characteristic of the key or keys depressed .in the code translating unit A12 having a power supply 32 and is passed to a relay storage unit A<SP>13</SP> of known kind having power supply 33. this corres ponding to letter position A<SP>2</SP>. If desired mean may be provided for diverting local or other heavy destination packets direct to a stack A<SP>11</SP> by means of a special key. The waiting position provides a means for rectifying a coding error since by pressing a "Cancel" key the code in A<SP>13</SP> is destroyed and the letter in A<SP>2</SP> passed to a reject box A<SP>14</SP> or the latter may be re-coded in A<SP>2</SP> without rejection being necessary. Corresponding to A<SP>3</SP> is a set of queue storage units A<SP>16</SP> to which the codes are transmitted simultaneously with the advancement A<SP>2</SP> to A3 of the letter by means of a queue control unit A<SP>15</SP>. A<SP>16</SP> may comprise a rotary input switch passing over rows of contacts which move one step further over when a signal is fed, corresponding to the number of letters in queue A<SP>3</SP>. The front letters in all the queues A3 ... F<SP>3</SP>, Fig. 1, may be loaded in a cyclic order at positions A<SP>4</SP>... F<SP>4</SP> by means not shown, controlled by means A<SP>17</SP> ... F<SP>17</SP>, Fig. 2. Alternatively preference may be given to the longer queues to reduce the risk of the queues becoming full. This would mean some blank spaces on the conveyer 30 thus requiring a higher speed or auxiliary conveyers to take some of the letters. Tone generator 37 converts the front code signal in the queue into one or a plurality of frequencies simultaneously with the loading, and these are passed by switching unit A<SP>18</SP>... F<SP>18</SP> corresponding to A<SP>17</SP>... F<SP>17</SP>, to a recording head A<SP>19</SP> ... F<SP>19</SP> adjacent magnetic recording tape 34, Fig. 1, moving in step with conveyer 30, A<SP>19</SP>... F<SP>19</SP> corresponding with A<SP>4</SP> ... F4. The letters are carried by conveyer 30 to unloading points 35, while the recordings pass to reproducing heads 36, each comprising an electric filter one of which passes the impulse to means for unloading the letter at the corresponding point 35 which the letter is just passing, or diverting it to another conveyer if required for further sorting in which case the impulse would be passed on and re-recorded on a second tape. An erasing head 50 removes the recordings after passing the last reproducing head. The capacities of the queue positions are such as to cater for maximum deviations expected from the average speed of the operators but in case an operator keeps up a fast speed long enough to fill all his queue positions his keyboard could be arranged to be locked temporarily. A diverting unit A20 is used when auxiliary sorting conveyers are employed, the diversions of letters and corresponding electricaldiversions being indicated by arrows A21, A24, the speeds of the auxiliary conveyers being calculated on probability considerations. Queue positions A3-F3 may comprise a chute 40, Fig. 3. divided into compartments 41 by gates 42, each compartment holding a letter 43. Means may be provided, not shown for opening the gates sufficiently long for each letter to pass to the next compartment on removal of the front letter in the queue. Alternatively the queue may comprise a rail track 44, Fig. 4, on which run a number of carriages 45 each being loaded by rollers 46 and then moving to join the queue for unloading by rollers 47. The queues and corresponding electrical storage equipment can be dispensed with if the speeds of the conveyers are much increased in which case the letters from each operator are sent direct to a gate which ensures that a free space exists on the conveyer before loading by electrical searching of the recording tape slightly in advance of the loading position. When a clear portion of the tape arrives the gate is opened to load one letter. The corresponding electric impulse is fed by having two sections of relay storage unit A13, one for holding the code in waiting position in case of rejection being necessary and one for holding the same code in 'gate' position from which it is fed to the recording head A19 through a control operated by the searching head. As the letter is actually passed to the loading point a time delay must be allowed for and may be made exact by inserting an earmarking frequency with the recording, slightly ahead of the loading position which is picked up by a reproducing head which loads the letter at the correct moment. There will be empty spaces on the conveyer which will have to travel fast enough to clear all the operator's outputs when working at maximum speed. Rare cases will occur when the search head will not find a space on the conveyer in the necessary minimum coding time and so is arranged to lock the keyboard of the operator. Where a plurality of conveyers is used, if alternate ones are conveying in opposite directions so that the first operator for one conveyer becomes the last operator for the next then assuming a large probability of equal distribution on the conveyers the outputs of all the operators will then be cleared equally quickly and the best economy of conveyer speed is possible.